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Introduction
Published in Armen S. Casparian, Gergely Sirokman, Ann O. Omollo, Rapid Review of Chemistry for the Life Sciences and Engineering, 2021
Armen S. Casparian, Gergely Sirokman, Ann O. Omollo
Ionization Potential/Energy: The ionization potential or energy is the amount of energy required to remove the outermost electron from a ground state atom in its gaseous state. This is known as the first ionization potential, usually measured in units of kilo-Joules/mole (kJ/mol) of atoms. This is usually relatively low for metal atoms which tend to lose electrons in a chemical reaction and form positive ions, and relatively high for nonmetallic atoms, which tend to attract electrons. Follow the red arrow in the Figure 1.1. For example, the lithium atom has a first ionization potential of 520 kJ/mol, meaning that this amount of energy would have to be applied to remove its outermost electron (i.e., its one 2S electron). This is a relatively low amount of energy when compared with a nonmetallic atom such fluorine, chlorine, or oxygen. If an atom has more than one electron, which can be removed, subsequent removal energies required are termed the “second” and “third” ionization potentials, which are normally, progressively higher.
Radiation Safety
Published in W. David Yates, Safety Professional’s Reference and Study Guide, 2020
Ionizing radiation occurs as the result of particles or electromagnetic waves having enough energy to detach electrons from atoms or molecules, thereby causing ionization of the atom. Ionization is defined as the process of converting a stable atom or molecule into a charged one through the gain or loss of electrons. Ionizing radiation is produced by the natural decay of radioactive material. This occurrence depends entirely on the energy of the particles or waves and not on the number. Ionizing radiation comes from radioactive materials, X-ray tubes, and particle accelerators and is present in the natural environment. There are two ways to cause ionization: direct and indirect. Direct ionization occurs as a result of charged particle interaction with matter. Indirect ionization occurs as a result of uncharged particle interaction with matter through collision. As mentioned, ionizing radiation comes in the form of particles or electromagnetic waves.
General Chemistry
Published in Steven L. Hoenig, Basic Chemical Concepts and Tables, 2019
Ionization energy is the minimum amount of energy needed to remove an electron from a gaseous atom or ion, and is expressed in kJ/mol. The IE increases going across the periodic table due to the fact that the principal energy level (principal quantum number) remains the same while the number of electrons increase, thereby enhancing the electrostatic attraction between the protons in the nucleus and the electrons. Going down the table the IE decreases because the outer electrons are now further from the nucleus and the protons.
Effect of brine type and pH on the interfacial tension behavior of carbonated brine/crude oil
Published in Journal of Dispersion Science and Technology, 2021
Saeed Zaker, Roohollah Parvizi, Ebrahim Ghaseminejad, Amin Moradi
In the second stage of this investigation, the effect of pH on IFT values is investigated since pH can affect the IFT values of binary solutions either acidic crude oil or non-acidic crude oil by synergistic or antagonistic effects. In more detail, it has been well proven that the composition of the aqueous phase is one of the most important and effective parameters on IFT modification greatly affected by pH value. For the cases with low pH values and using Le Chatelier’s principle, the net interface charge will be positive while at higher pH values it would be negative.[27,28] In detail, Equation (2) indicates a weak acid/base reaction in water for acid groups like carboxylic acids . where AH represents the nonionic form of the acid groups and A- is the ionized form of the acid groups. The degree of dissociation of acids and bases is expressed in terms of dissociation constant also known as ionization constant (Ka). This constant expresses the concentration ratio of the molecules in ionic form to nonionic form at the state of equilibrium, and is given as follows for Equation (2):[29] where square brackets represent the concentration of each species,
Molecular engineering of the efficiency of new thieno[3,2-b]thiophene-based metal-free dyes owning different donor and π-linkers groups for use in the dye-sensitised solar cells: a quantum chemical study
Published in Molecular Physics, 2021
Hossein Roohi, Nafiseh Motamedifar
To further elucidation of the charge transfer property of the dyes, ionisation potential (IP) and electron affinity (EA) are computed for the injection of holes and electrons mechanisms [70]. IP and EA are calculated in two ways. (1) Via difference between total energies of the neutral (Eneutral) and ionic systems (Ecation, Eanion) obtained from optimised molecular structures [71] and (2) based on Koopman’s theorem that IP and EA are approximated as the negative value of the energy for the lowest unoccupied molecular orbital (HOMO) and the negative value of the highest occupied molecular orbital, respectively [72]. The calculated results at DFT/B3LYP/6–31++G(d,p) level of theory are listed in Table 2. Ionisation potential is referred to the energy required for the removal of an electron from the neutral molecule, i.e. the lower the IP, the easier is to release an electron and thus to create a hole [73]. The electron affinity is defined as the difference between the energies of the neutral molecule and the anionic form of the molecule in their lowest states, i.e. it denotes the binding energy of an electron to the molecule [74]. The EA of the dyes allows the recombination process between the injected electron and the oxidised dye species, where an electron in the CB conductor can be captured by the adsorbed sensitiser entity [75]. Therefore, the small EA and IP values for dyes are favourable for the migration of electron efficiently to the conduction band.
Influence of Carrier–Carrier Interactions on the Noise Performance of Millimeter-Wave IMPATTs
Published in IETE Journal of Research, 2019
Prasit Kumar Bandyopadhyay, Arindam Biswas, A. K. Bhattacharjee, Aritra Acharyya
Figure 2 illustrates the bar graphs showing the avalanche region width (xA) of 94, 140 and 220 GHz DDRs obtained from DC simulation by considering ionization rate data obtained from both the analytical model of Acharyya et al. [2,3] and the experiential relations of Grant [15]. It is clearly observable that xA gets widen when the effect of inter-carrier collisions has been incorporated in the simulation via the ionization rate model of Acharyya et al. [2,3]. The reason behind it can be explained as follows. The αe vs. ξ and αh vs. ξ plots of Si presented in the earlier report [1] show that impact ionization rates deteriorate significantly with the increase of carrier densities [2,3] due to enhanced energy loss per unit length as a result of increased amount of inter-carrier interactions. The ionization rate represents the amount of ionizing collisions take place due to unit distance travel of a single carrier (electron or hole). Lower ionization rate signifies more distance have to be travelled by that carrier in order to face same number of ionizing collisions. That is why the multiplication zone or avalanche region of the diode has to be expanded to cause the same amount of charge multiplication leading to breakdown of the device. Greater doping concentrations in both n- and p-epitaxial layers of the diodes operating at higher mm-wave frequencies cause higher probability of carrier–carrier collisions within the active region of those. Consequently, broadening of xA is observed to be increased as the frequency of operating of the device is increased.